samples/vfio-mdev/README.rst

Source file repositories/reference/linux-study-clean/samples/vfio-mdev/README.rst

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samples/vfio-mdev/README.rst
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Using the mtty vfio-mdev sample code
====================================

mtty is a sample vfio-mdev driver that demonstrates how to use the mediated
device framework.

The sample driver creates an mdev device that simulates a serial port over a PCI
card.

1. Build and load the mtty.ko module.

   This step creates a dummy device, /sys/devices/virtual/mtty/mtty/

   Files in this device directory in sysfs are similar to the following::

     # tree /sys/devices/virtual/mtty/mtty/
        /sys/devices/virtual/mtty/mtty/
        |-- mdev_supported_types
        |   |-- mtty-1
        |   |   |-- available_instances
        |   |   |-- create
        |   |   |-- device_api
        |   |   |-- devices
        |   |   `-- name
        |   `-- mtty-2
        |       |-- available_instances
        |       |-- create
        |       |-- device_api
        |       |-- devices
        |       `-- name
        |-- mtty_dev
        |   `-- sample_mtty_dev
        |-- power
        |   |-- autosuspend_delay_ms
        |   |-- control
        |   |-- runtime_active_time
        |   |-- runtime_status
        |   `-- runtime_suspended_time
        |-- subsystem -> ../../../../class/mtty
        `-- uevent

2. Create a mediated device by using the dummy device that you created in the
   previous step::

     # echo "83b8f4f2-509f-382f-3c1e-e6bfe0fa1001" >	\
              /sys/devices/virtual/mtty/mtty/mdev_supported_types/mtty-2/create

3. Add parameters to qemu-kvm::

     -device vfio-pci,\
      sysfsdev=/sys/bus/mdev/devices/83b8f4f2-509f-382f-3c1e-e6bfe0fa1001

4. Boot the VM.

   In the Linux guest VM, with no hardware on the host, the device appears
   as  follows::

     # lspci -s 00:05.0 -xxvv
     00:05.0 Serial controller: Device 4348:3253 (rev 10) (prog-if 02 [16550])
             Subsystem: Device 4348:3253
             Physical Slot: 5
             Control: I/O+ Mem- BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr-
     Stepping- SERR- FastB2B- DisINTx-
             Status: Cap- 66MHz- UDF- FastB2B- ParErr- DEVSEL=medium >TAbort-
     <TAbort- <MAbort- >SERR- <PERR- INTx-
             Interrupt: pin A routed to IRQ 10
             Region 0: I/O ports at c150 [size=8]
             Region 1: I/O ports at c158 [size=8]
             Kernel driver in use: serial
     00: 48 43 53 32 01 00 00 02 10 02 00 07 00 00 00 00

Annotation

Implementation Notes